This invention relates to optical product inspection, and more particularly to inspecting products optically in order to ensure that they include required image information such as certain text.
Automated inspection of visual appearance is desirable or required for many products, especially those made in large quantities and/or at high speeds. For example, in the United States, cigarette packages are required to bear a label known as the Surgeon General's warning which must be changed every three months and which may vary in configuration from cigarette brand to cigarette brand. It would be advantageous to be able to inspect each package to ensure that it contains the proper message and message configuration, that the message is properly located, that the message is legible (e.g., not smeared), etc. However, cigarette packages are typically made at such high speeds (e.g., currently about 720 packages per minute) that such inspection is only practical if automated. Optical character recognition is a technology which might be considered as a solution to this problem. However, because it is not necessary to actually read and recognize each individual character, optical character recognition involves gathering and processing more information than is really needed. Accordingly, optical character recognition tends to be too expensive and/or too slow for this application.
In view of the foregoing, it is an object of this invention to provide improved methods and apparatus for optically inspecting products for the presence, correctness, and acceptability of visual information, and especially textual information.
It is a more particular object of this invention to provide methods and apparatus, characterized by very high speed and relatively low cost, for optically inspecting products to ensure that predetermined visual information, and especially textual information, is present, properly located, and acceptable.